The present invention is particularly applicable for use in connection with welding wire and, therefore, the invention will be described with particular reference to a package containing a large quantity of welding wire stored therein as a coil containing many convolutions formed in layers. However, the invention has broader applications and may be used with any type of wire or other wirelike materials.
It is, of course, well known that welding is an effective method of joining metal components. Further, it is well known that utilizing a welding wire as a consumable electrode in the welding process enhances the weld. Accordingly, it is desirous to package welding wire so that it can be cost effectively utilized. Furthermore, welding applications wherein large quantities of welding wire are consumed necessitate welding wire packages which contain large quantities of a continuous welding wire. As a result, large welding wire packages have been created for these applications which allow for a significant amount of welding run time before the operation must be shut down to restring a new package of welding wire. This is particularly important for automated or semi-automated welding operations.
Bulk packaging of MIG wire is gaining popularity in both automated and semi-automated welding applications due to the reduced down time necessary to change and restring a new package of welding wire. Further, it is important to have reliable wire payout or dispensing from the welding wire package without wire tangling or wire flip/wander. Each tangle can potentially shut down an entire manufacturing line and reduces production yield. In this respect, in order to work in connection with the wire feeder of the welder, the welding wire must be dispensed in a non-twisted, non-distorted and non-canted condition which produces a more uniform weld without human attention. It is well known that wire has a tendency to seek a predetermined natural condition which can adversely affect the welding process. Accordingly, the wire must be sufficiently controlled by the interaction between the welding wire package and the wire feeder.
Wood or plastic reels are one form of bulk packaging. While reel packaging has a low tendency of tangling, it can occupy a large amount of floor space and is not easily changed over due to the time necessary to set up the dereeler equipment. Furthermore, the welding wire on the reel is exposed to the environment of the manufacturing operation which is often dusty and/or dirty. Another disadvantage of the reel type container is that they must be a rigid structure to hold the weight of the wire and allow the wire to pivot about an axis. As a result, disposing of the spent wire reel is costly.
Drum or box wire packages have been developed which protect the welding wire from the manufacturing environment and which can be disposed of at a lesser cost. The welding wire is coiled into the drum or box package in a loosely wound wire stack or coil consisting of many convolutions of wire which are often not as structurally stable as the wire convolutions of the reeled wire. As a result, it is also important to control the wire within the package in addition to the payout of the wire from the package in order to reduce twisting, tangling or canting of the welding wire. This condition is worsened with larger welding wire packages which are favored in automated or semi-automated welding operations. Furthermore, abuse during shipping and handling of the soft drum or box container often disrupts the uniform spacing or stacking of each convolution in the wire stack. Therefore, while drum or box wire packages provide some advantages over reeled wire, they are more susceptible to tangling.
A retainer ring can be used to both hold down the upward springing effect of the wire convolutions and to help control the outflow of the welding wire from the packaging without introducing additional distortions in the welding wire. As stated above, the drum or box welding wire package houses a coil of welding wire having many layers of wire convolutions laid from the bottom to the top of the package. These convolutions include an inner diameter and an outer diameter wherein the inner diameter is substantially smaller than the outer diameter. The memory or natural cast of the wire causes constant force in the convolutions of wire which is directed outwardly such that the diameter of each convolution is under constant influence or force to widen. The outer wall or walls of the wire welding package prevent such widening. However, when the welding wire is dispensed from the package, the walls of the package lose their influence on the wire and the wire will attempt to assume its natural cast. This causes the portion of the wire which is being withdrawn from the package to loosen and tend to spring back into the package thereby interfering and possibly becoming tangled with other convolutions of wire. In addition, the natural cast and/or twist in the wire causes the convolutions of welding wire to spring upwardly. The retainer ring controls these conditions in several ways. The weight of the retainer ring prevents the convolutions of wire from springing upwardly and works in connection with the wire package to control the outward spreading effect of the convolutions of wire. The shape of the retainer ring helps control the payout or dispensing of the wire from the package.
The retainer ring is positioned on the top of the wire coil such that the weight of the ring counteracts the upward lifting force of the wire coils. In prior art packaging, the retainer ring, wire coil and container all had the same general shape. In wire drums, the welding wire is positioned in the drum such that the wire engages the inner drum wall around the entire drum. This packaging design makes the clearance between the retainer ring and the inside of the drum a critical dimension. If the clearance is too small, the retainer ring will not reliably fall as the height of the wire coil is reduced during wire dispensing. For one, if the retainer ring becomes misaligned with respect to the drum wall it can become jammed with the packaging. This condition can happen when the retainer ring is lifted on one side by the wire movement during payout, when the wire coil is not level, or when the ring itself is not flat. Another problem with this design is that due to the minimal clearance between the ring and the drum, the drum outer wall must be nearly a perfect cylinder or the retainer ring can become lodged by the imperfections. Imperfections in the drum outer wall can be caused by a manufacturing problem or damage during the shipment of the welding wire package. Furthermore, shrink wrapping the drum for the shipment can also cause distortions in the outer wall of the drum. As a result, the low clearance ring design causes a large amount of down time necessary to continuously free a jammed or hung-up ring.
In order to reduce the tendency of the retainer ring jamming within the welding wire package, the clearance between the peripheral edge of the retainer ring and the inner surface of the outer wall of the welding wire package has been increased in some prior art packages. This can virtually solve the jamming problem. However, in a large clearance ring design, the retainer ring does not completely cover the top of the wire coil. During payout, the wire convolutions on the top layer of the wire coil tend to move outwardly due to the natural cast of the wire thereby causing the wire convolutions to expand and extend out beyond the outer periphery of the ring. As a result, the wire convolutions can pop upwardly between the outer periphery of the retainer ring and the drum wall which can severely tangle the welding wire and cause significant down time. This condition is worsened by the fact that the welding wire, which is pulled from the center of the retaining ring, has a tendency to urge one side of the retainer ring outwardly against the drum wall. This shifting enlarges the gap along the back side of the retainer ring disadvantageously increasing the likelihood that one or more convolutions of wire may spring upwardly through the gap. This condition is called “back side tangle” and can damage the retainer ring. As can be appreciated, a damaged retainer ring which is tangled amongst several convolutions of wire can cause significant down time. Furthermore, the large clearance retainer ring design can also be influenced by imperfections in the drum outer wall configuration. Therefore, in order to reduce the tangle rate, it is also necessary to maintain strict controls over the configuration of the outer drum packaging.
In an effort to overcome these problems, prior art retainer rings were designed to utilize resilient members which engage the inner surface of the welding wire drum. This particular design allows the use of a large clearance retainer ring while still protecting the outer convolutions of the welding wire coil to prevent the wire convolutions from springing outside the peripheral edge of the retainer ring. However, the frictional engagement between the retainer ring and the inner container walls, introduced drag into the system which adversely reduces the downward force produced by the retainer ring. The drag produced by the flexible members can also adversely jam the retainer ring above the wire coil, thereby reducing its control on the wire payout. In order to overcome the retainer ring drag, the weight of the retainer ring is increased or separate weights must be used. Furthermore, this ring design is still influenced by imperfections or damage to the outer drum of the wire package. As can be appreciated, a dent in the drum which is engaged by one of the resilient members, can stop the downward travel of the retainer ring. Further, the flexible members can break or crack causing tangling of the welding wire.
As stated above, the ability to inexpensively dispose of the welding wire package is also important. While rigid package designs can be used to reduce the likelihood of shipping damage, reduce coil shifting during shipment, and enhance the stackability of the package, rigid packages are difficult and expensive to dispose of. In welding operations which consume significant quantities of welding wire, package designs which are easily movable without significant concern to outer package damage and which are inexpensive to dispose of can play a significant role in the support operations for the welding process.